sorting/randomizing text blocks separated by empty lines

Given a document with text blocks separated by empty lines:

```
foo
chunk one

bar
chunk two

baz
chunk three
```

I need to both (for different purposes) 1) sort the blocks by their
first lines and then 2) randomize the blocks by their first line.

How might one (I) do this?

c
--
Chris Lott <chris@chrislott.org>

--
--
You received this message from the "vim_use" maillist.
Do not top-post! Type your reply below the text you are replying to.
For more information, visit http://www.vim.org/maillist.php

---
You received this message because you are subscribed to the Google Groups "vim_use" group.
To unsubscribe from this group and stop receiving emails from it, send an email to vim_use+unsubscribe@googlegroups.com.
For more options, visit https://groups.google.com/groups/opt_out.